I have a 95n that I changed the cat and O2 sensor after the cat. A few days later it started to have like a serge/buck at around 70mph. the next day when it serged/bucked, then I heard a hissing noise (found that it started to leak where the cat and y pipe where together). Had a code P1133 and P0133. I fixed the leak BUT then it started to run worst. The motor sounds good, It just doesn't want to go down the road. I thought maybe it was just my luck that something happened to the tranny at the same time. So I changed the tranny filter, fluid looked normal. and still ran like crap. It then had a code of P0304, So I bought another O2 and installed it. It drove better down the road until it got warmed up then it couldn't get out of it's own way and was bucking and surging. I am at a complete loss as to what the issue is. Could it be a bad cat?